The premise is simple – you tune your guitar and then play notes or chords. The app (which runs on a phone or your browser) senses your strum and lets you move on or asks you to repeat the notes.

Generally, rockabilly makes heavy use of the well-known I-IV-V blues progression. In the key of E the chords are E-A-B; in the key of A it's A-D-E, and 6th, 7th and 9th versions of these major chords ...